[Talk-us-massachusetts] Fwd: GPS on Benchmarks Campaign from the National Geodetic Survey

[Greg Troxel]

Andy Anderson <aanderson at amherst.edu> writes:

> The implication is that they don’t have good information about the
> location of most of these.

I was skeptical of this suggestion (that navigation-solution positions
owuld be helpful), but their page indeed says they want non-survey-grade
measurements of marks that are marked "SCALED" meaning they guess the
location from a topo map.  I don't think there are that many of those.

They also want recovery notes for marks that have not been recovered in
30 years.

They do want survey-grade ellipsoidal height measurements of benchmarks.

https://www.ngs.noaa.gov/GPSonBM/
https://www.ngs.noaa.gov/GPSonBM/observe.shtml

You can get a shapefile of all the marks via the database search page at

https://www.ngs.noaa.gov/datasheets/index.shtml

I was able to load that layer into QGIS with an OSM basemap.
I was then able to do category-based symbolization and find the ones
marked "scaled".  An example of scaled is

https://www.ngs.noaa.gov/cgi-bin/ds_mark.prl?PidBox=MY2109


There are fairly few scaled ones, and from a very quick look they seem
to lean to true benchmarks (vertical control) along roads and railroads.

I'll send a screenshot offlist to Andy and Peter and happy to send it to
anyone else who wants it; it's too big for the list  (not a complaint!).

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